1. Field of the Invention
This invention generally relates to a dampening disk assembly. More specifically, the present invention relates to a dampening disk assembly having circumferential gaps for preventing a predetermined friction mechanism from operating when small vibrations occur in a greater torsion angular range of the torsion characteristics.
2. Background Information
A clutch disk assembly or dampening disk assembly is often used in a clutch of a vehicle. The clutch or dampening disk assembly has a clutch function for coupling and/or uncoupling a flywheel of the engine to the transmission shaft, and a dampening function for absorbing and dampening torsion vibrations transmitted from the flywheel. Generally, vibrations of a vehicle include rattling during idling, rattling during driving (due to acceleration and deceleration), and tip-in/tip-out (low frequency vibrations). The dampening function of a clutch or dampening disk assembly eliminates these rattling and vibrations.
Rattling during idling is a rattling noise from the transmission that occurs while the vehicle is for instance waiting for the signal, the gear is in neutral and the clutch pedal is let free. The rattling occurs because engine torque is small during idling, and combustion of the engine generates a relatively large torque. As a result, an input gear of the transmission and a counter gear collide into each other, and generate rattling noises.
Tip-in/tip-out rattling (low frequency vibrations) is a back and forth movement of a vehicle that occurs when the driver pushes or let go of the acceleration pedal suddenly. Tip-in/tip-out rattling occurs when the rigidity of the drive transmission is low. A torque transmitted to tires is transmitted back from the tires, and then the torque is retransmitted to the tires. As a result, the vehicle temporarily moves back and forth.
Rattling during idling also occurs when a torque transmitted in the clutch disk assembly is almost zero. To prevent this type of rattling during idling, the torsion rigidity of the clutch disk assembly should be low for such torque. On the other hand, the clutch disk assembly should have a higher rigidity to prevent tip-in/tip-out rattling.
In view of the aforementioned problems, there has been known a clutch or dampening disk assembly, which utilizes two kinds of springs to obtain two levels of torsion characteristics. In the lower torsion angular range, the clutch or dampening disk assembly has low torsion rigidity and low hysteresis torque, such that rattling during idling can be prevented. In the higher torsion angular range, the clutch or dampening disk assembly has high torsion rigidity and high hysteresis torque, such that front and back movements during tip-in/tip-out rattlings are sufficiently dampened.
There has also been known a dampening mechanism in which a friction mechanism is prevented from operating when small vibrations from fluctuations in engine combustion are transmitted in a higher torsion angular range, even though the friction mechanism is adapted to function in the higher torsion angular range. In this manner, the clutch disk assembly dampens small vibrations by generating small hysteresis torque.
In a conventional clutch disk assembly, a resin-made friction member is coupled to, for instance, a retaining plate, such that the friction member and the retaining plate are rotatable to each other within a predetermined angular range. Therefore, when small vibrations occur in the higher torsion angular range of the torsion characteristics, a cone spring slides against the retaining plate. Since the cone spring and the retaining plate are both made of metals, hysteresis torque generated in this case is not adjustable. As a result, hysteresis torque of certain types of vehicles is not adjusted to an adequate level for small vibrations.
In view of the above, there exists a need for a clutch or dampening disk assembly which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.